Arrhythmogenesis in heart failure

Area of Science:

• Cardiology
• Physiology
• Molecular Biology

Background:

• Heart failure (HF) is a complex condition often associated with arrhythmias.
• Understanding the mechanisms underlying ventricular arrhythmias in HF is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the occurrence and underlying mechanisms of nonsustained ventricular tachycardias (NSVT) in a rabbit model of heart failure.
• To explore the role of delayed afterdepolarizations (DADs) and triggered activity in the development of arrhythmias in failing hearts.

Main Methods:

• A rabbit model of heart failure was created using combined pressure and volume overload.
• Microelectrode recordings were performed on ventricular trabeculae from both failing rabbits and human patients with end-stage heart failure.
• Electrophysiological parameters, including extracellular potassium concentration and the presence of norepinephrine, were manipulated.

Main Results:

• Nonsustained ventricular tachycardias developed in a significant portion of the failing rabbit models.
• Delayed afterdepolarizations and triggered activity were observed in approximately half of the preparations under specific conditions (norepinephrine, 3 mM extracellular K+).
• Spontaneous calcium release from the sarcoplasmic reticulum was identified as the underlying cause of DADs and triggered activity.

Conclusions:

• Delayed afterdepolarizations and triggered activity, mediated by spontaneous calcium release, contribute to ventricular arrhythmias in heart failure.
• These electrophysiological abnormalities are exacerbated by norepinephrine and low extracellular potassium concentrations.
• The findings provide insights into the arrhythmogenic mechanisms in failing myocardium, relevant to both animal models and human patients.